The objective of this project is to isolate and characterize anticarcinogenic constituents from the fungus plant Ganoderma lucidum using bioassay-directed fractionation. The approach to the discovery of potential chemopreventive agents is based on the observation that the chemical components in G. lucidum were found to inhibit significantly benzo(a)pyrene-induced tumorigenesis in mice. The specific aims are 1) to isolate the anticarcinogenic constituents from G. lucidum, 2) to determine the structures of these compounds based on spectral analysis, 3) to evaluate these compounds by using assays of inhibition of DNA methylation and aberrant crypts formation, and 4) to establish preliminary structure-activity relationships based on structural modification of the compounds isolated and to select the leads for further development in the phase II.